The present invention relates generally to methods and apparatuses for folding paper and more particularly to a method and apparatus for folding a continuous web of paper having a transverse slit.
Method and apparatuses of the type to which the present invention relates are used in the mass production of large volumes of printed booklets. In such methods, high speed equipment is used to print copy repetitively on a continuous web of paper advancing in a longitudinal direction along a predetermined path. The continuous web of paper has a longitudinally extending marginal part and a longitudinally extending second part located alongside the marginal part. After copy has been printed on the web, the web is subjected to a folding operation in which the marginal part of the web is folded out of the plane of the web and then into lapping relation with the second part of the web. Lines and strips of adhesive may be applied to the web at preselected locations thereon, before folding, so that, as a result of the folding operation, the marginal web part is adhered to the second web part adjacent a longitudinal edge of the former, and along a series of longitudinally spaced lateral lines of adhesion to form a series of pockets extending in end to end relation longitudinally along the web.
For reasons sometimes connected with manufacturing operations occurring at a location downstream of the location or station where the folding is performed, the web is often-times subjected to tension at the folding station. During the folding operation, when the marginal part of the web is folded out of the plane of the web, some or all of the tension which had been exerted on the marginal part of the web is exerted on the second part of the web.
When the method and apparatus described above are used to manufacture a booklet-type ticket-holder, such as for holding an airline ticket, a transverse slit is cut in the second part of the web, and the cutting occurs at a location upstream of the folding station. The transverse slit is used for inserting a ticket through the slit into the pocket formed when the marginal web part is adhered to the second web part as a result of the folding operation.
As noted above, when a tensioned web is subjected to a folding operation of the type described above, there is an increase in the tension exerted against the second web part, and when the second web part has a transverse slit therein, there is a possibility of transverse tearing from the slit, across the second part of the web, during the folding operation. This, of course, is undesirable.